I completed a Jack's #2 Copper treatment in late October when the water temperature was in the 70's. Shortly after it was completed, we had a cold snap and it dropped the pool temperature quickly below 65 degrees, and it's not 52 degrees. The instructions from Jack's was that post-treatement, to expect FC readings to be zero, and to measure chlorine levels via TC (FC+CC). I also understand that the colder water temperatures may increase the time to continue this practice until the FC readings come back.
It's been 2 months now and I still get a FC reading of zero, and a CC reading of 3-4ppm. My CYA was also low and I had a couple of pucks remaining so I have a couple floaters in there to add CL and CYA - so there is a source of CL.
Given all this, I am good by continuing to measure CL using TC until the water warms up?
Here are my current readings:
CH=??? (reads 400ppm, but that's higher than before Jack's treatment - where it was 300ppm)
Borates = 40
Temperature = 52 degrees
Salt = 2600 (but SWG currently off for the winter)
I also add Jack's purple to 10ppm to keep copper in check (it comes from my water source)